Wireless communications provide a means of communicating across a distance by means of electromagnetic signals. In an environment of plural electrical signals the signals may interfere, thereby rendering the signals difficult to detect reliably. This may particularly be the case in multi-user systems where signals of different users may interfere. By allocating signals of different users to different channels or channel resources, such interference may be reduced or eliminated.
Due to the limited availability of channel resources, e.g. in terms of radio frequency spectrum or light spectrum, to cover a surface may require some of the channel resources to be re-used at different locations along the covered surface. For this purpose available channel resources may be divided into one or more groups. Further, the surface to be covered by wireless services or communications is divided into a plurality of smaller, preferably but not necessarily non-overlapping, areas. These smaller areas are referred to as cells, and are generally defined in terms of the wireless coverage, such as radio coverage of a channel group of a particular radio transmitter of the cell, where the transmitter forms part of a base station providing wireless coverage of the cell.
The number of groups is associated with particular reuse-patterns of preferred allocation of channel groups to the various cells (or part of cell) covering the surface of interest. Such reuse is referred to as K-reuse, where K represents the number of groups of such reuse.
3GPP TR 25.814 V7.1.0, Technical report; 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical layer aspects for evolved Universal Terrestrial Radio Access (UTRA) (Release 7), France, September 2006, is related to the 5 technical report for physical layer aspect of the study item “Evolved UTRA and UTRAN” and considers in sections 7.1.2.6 and 9.1.2.7 “Inter-cell interference mitigation” three basic approaches to inter-cell interference mitigation:                Co-ordination/avoidance        Inter-cell-interference randomization, and        Inter-cell-interference cancellation.        
For the uplink, also                Frequency domain spreading        
is considered.
In addition, the use of                Beam-forming antenna solutions at the base station        
is a general method that can also be seen as a means for downlink inter-cell-interference mitigation.
As regards the coordination/avoidance, the 3GPP technical report concludes that the common theme of inter-cell-interference co-ordination/avoidance is to apply restrictions to the resource management (configuration for the common channels and scheduling for the non common channels) in a coordinated way between cells. These restrictions can be in the form of restrictions to what time/frequency resources are available to the resource manager or restrictions on the transmit power that can be applied to certain time/frequency resources. Such restrictions in a cell will provide the possibility for improvement in SIR, and cell-edge data-rates/coverage, on the corresponding time/frequency resources in a neighbor cell.
In the 3GPP technical report, for static interference co-ordination reconfiguration of the restrictions is done on a time scale corresponding to days. The inter-node communication is very limited (set up of restrictions), basically with a rate of in the order of once per day, whereas for semi-static interference co-ordination, reconfiguration of the restrictions is done on a time scale corresponding to seconds or longer. Inter-node communication corresponds to information needed to decide on reconfiguration of the scheduler restrictions (examples of communicated information: traffic-distribution within the different cells, uplink interference contribution from cell A to cell B, etc.) as well as the actual reconfiguration decisions. For semi-static interference co-ordination, signaling rate is in the order of tens of seconds to minutes.
Arne Simonsson, “Frequency Reuse and Intercell Interference Co-ordination in E-UTRA”, VTC 2007-Spring, IEEE 65th, 22-25 Apr. 2007, pp. 3091-3095, evaluates some basic schemes of intercell interference co-ordination by means of simulations. Anticipating a uniform user distribution, it is concluded that of the static schemes 1-reuse performs the best for wideband services and that a dynamic scheme is required to improve compared to 1-reuse.
Wang et al., “An Interference Aware Dynamic Spectrum Sharing Algorithm for Local Area LTE-Advanced Networks”, VIC 2009-Fall, 2009 IEEE 70th, 20-23 Sep. 2009, discloses a dynamic spectrum sharing algorithm to minimize inter-cell interference. The algorithm operates in a self-organized manner without the need of any centralized control and is evaluated in the context of LTE-Advanced Downlink transmission. Average cell throughput, average cell load, cell edge user throughput and spectrum allocation interval are used as performance metrics for the evaluation.
D. Renaud and A. Caminada, “Evolutionary Methods and Operators for Frequency Assignment Problem”, Speed Lip Journal 11(2), pp. 27-32, Proceedings 22nd Workshop, 18-19 Sep. 1997, briefly describes evolutionary methods in a context of interference minimization. Renaud and Caminada state that a frequency assignment problem may be understood as an optimization problem where the subject is to minimize co5 channel and adjacent-channel interference and further states that the optimization problem may be reduced to the graph coloring problem which is an NP-complete combinatorial problem. For the genetic coding of their evolutionary method, a chromosome representation for the frequency assignment problem is illustrated, where the length of the chromosome is equal to the total traffic of the network and one chromosome in each gene corresponds to a particular frequency in a particular cell.
Y. Xiang et al. “Inter-cell Interference Mitigation through Flexible Resource Reuse in OFDMA based Communication Networks”, In Proc. 13th European Wireless Conference EW2 007, examines flexible radio resource reuse schemes for the downlink. The cell capacity under some presented reuse schemes is estimated and compared.
Texas Instruments: “Inter-Cell Interference Mitigation for EUTRA”, 3GPP TSG RAN WGJ, R1-051059, 10-14 Oct. 2005, proposes frequency scheduling coordination for interference avoidance near the cell edge in an attempt to provide a service quality largely independent of UE (User Equipment) location. A soft reuse principle is applied for the allocation of frequency sub-bands in adjacent cells. This allocation is achieved through semi-static network coordination taking into account the traffic load, i.e. the distribution (location and/or transmit power requirements) and throughput requirements of UEs near the edge of each cell.
The 3GPP proposal concludes that a semi-static coordination of reserved frequency sub-bands among cells is preferable for LTE in order to more effectively address the varying throughput requirements and UE populations near the cell edge. Semi-static coordination may be achieved, for example, by the Node Bs communicating to the RNC their throughput requirements near the cell edge and with the RNC communicating to the Node Bs the partition of corresponding reserved frequency sub-bands. Combining frequency and time scheduling allows for even better flexibility in resource allocation and managing dynamic traffic loads near the cell edges thereby improving throughput performance. Similar to frequency coordination, time coordination can be static or semi-static with the latter allowing for more efficient resource allocation. FIG. 1 illustrates an example cell pattern for K=3 channel groups. Cell 1 is allocated a first reserved frequency sub-band, Cells 2, 4, and 6 are allocated a second reserved frequency sub-band, and Cells 3, 5, and 7 are allocated a third reserved frequency sub-band. Certain frequency sub-bands are reserved in each cell for use by UEs near the edge (UEs requiring high transmission power). UEs located toward the cell interior have available for scheduling the remaining frequency sub-bands and possibly some of the reserved sub-bands, if they were not allocated to UEs near the cell edge. The size of the reserved frequency sub-bands depends on the traffic load near the cell edge.
Texas Instruments: “Performance of Inter-Cell Interference Mitigation with Semi-Static Frequency Planning for EUTRA Downlink”, 3GPP TSG RAN WG1, R1-051059, 13-17 Feb. 2006, considers performance of ICI mitigation based on the soft reuse principle for the allocation of reserved frequency sub-bands in adjacent cells in proposal R1-051059 above.
The inventor of the present invention finds that: Not at least during an early phase of newly commissioned networks, user distribution tends to be far from uniform both within cells and considering an area corresponding to plural cells. In order to facilitate establishment of new networks and also to run well-established networks efficiently, network equipment need allow efficient operations despite non-uniform user or traffic distributions. Cited prior art does not identify or benefit from the fact that users e.g. being further away from their serving base station may demonstrate a greater variance in experienced interference, e.g. downlink interference from surrounding base station serving user's of other cells as compared to users closer to their serving base stations.